Recently, it been desired to be small and to have a high power density as a power source for vehicles and cell phones for secondary batteries, in order to protect the environment. For that reason, the development of various members has been promoted in various secondary batteries including a lithium ion battery having an active material with a high power density.
A current collector, which is one of the members, is typically formed using a metal foil. For example, in Patent Document 1, it is attempted to improve the balance between the conductivity and the brittleness by using a current collector formed of a conductive resin including carbon and two or more kinds of polyolefin copolymers in a redox flow type secondary battery.